Around 30 students from the University of Technology in Darmstadt, Germany, led by professors Thomas Hartkopf (renewable energies) and Manfred Hegger (architecture), have won the one-week international “Solar Decathlon 2007” held in Washington D.C. Sponsored by the U.S. Department of Energy, the competition awards prizes to homes that are particularly energy efficient and sustainable. The students integrated into their 80 square-meter house 50 square meters of BASF’s innovative Micronal® PCM SmartBoard™ gypsum wall boards plus a Micronal PCM SmartBoard-modified chilled ceiling developed by Zwickau-based Ilkazell Insulation Technology GmbH.

The Darmstadt team held their own against 19 universities from the United States, Canada and Spain. When designing their award-winning house, the students wanted above all to develop a home that consumed as little energy as possible but nevertheless provided maximum comfort. This is precisely what Micronal PCM SmartBoard offers: the gypsum wall board contains the phase change material Micronal PCM in the form of microscopically small wax spheres in an acrylic polymer shell. At a pre-defined switching temperature of 23°C, the wax melts and absorbs excess energy from the room in the form of heat.

In the design of the Darmstadt solar house, the phase change materials played a key role in maintaining the required indoor temperature at a constant level. In order to transport the heat stored in the melted wax out of the house, the students used a highly sophisticated system: during the day they piped cold water at a temperature of 16°C from a water tank through the chilled ceiling elements made by Ilkazell, in this way actively cooling the house. At night, they piped the heated water onto the solar cells installed on the roof, where part of it evaporated. The ensuing evaporative heat loss cooled the remaining water, which was piped back into the water tank.

Additional advantages of the BASF product: by installing 15 mm SmartBoard gypsum wall boards, the Darmstadt designers stored as much heat in their solar home as a 90 mm concrete wall. The gypsum wall boards also provided the architectural freedom of design necessary for the competition.